I agree, X is one of the less compelling applications for native IPv6 support given that just about everyone I know already tunnels it over an SSH connection. SSH has had IPv6 support for some time, so you can easily SSH into a machine with IPv6 and invoke an X session with the IPv4 connections on each end that never leave the local machines.
SSH tunneling works so well for X that I wouldn't even mind if all IP support were removed, as long as there was still a way (e.g., UNIX domain sockets) to connect the SSH daemons to the X server and client on each end.
That said, it's still a good thing for X to support IPv6, just in case someone wants to use it. Every Internet application should support both IPv4 and IPv6.
There are a few important situations where IPv6 is already The Right Answer.
First on the list is accessing servers behind a NAT. Wouldn't you like to connect directly to the multiple Linux boxes behind your NAT box without having to first log into the NAT and out again, or having to set up ad-hoc port forwarding kludges? Configure 6to4 on your NAT (easy if it's a Linux box) and you can establish a direct logical end-to-end IPv6 ssh connection even if the path in the middle is IPv4 only. Works great for me. I have been maintaining my parents' network in exactly this fashion for some time now.
Also on the list is VoIP. Look at all the hassles involved in running H323 from behind a NAT. (SIP may be more NAT-friendly, I haven't investigated it yet.) If only H323 supported IPv6, life would be so much easier.
But the real killer app for IPv6 will be cell phones. If cell phones are to implement true VoIP, there is simply no alternative to IPv6 because there are simply far too many cell phones in the world for the number of available IPv4 addresses.
Basically, IPv6 is all about wiping out the NAT plague and restoring the end-to-end model that originally made the Internet great. That's exactly opposite to the claim you make in your subject line. If you don't use NATs, or if you're unimaginative enough to think that you'll never need to do what they make difficult or impossible, then you probably won't be excited by IPv6. But eventually you'll probably discover why IPv6 is inevitable, even though it will have to coexist with IPv4 for a very long time.
Re:More to it than meets the eye
on
Cisco's Wi-Fi Phone
·
· Score: 4, Interesting
That answers the question I was about to ask. Cisco has really crippled their VoIP phones by having them speak only their proprietary "skinny" protocol. Without an expensive and proprietary server, these phones are totally useless. At the very least, these phones ought to speak basic H.323/SIP/whatever without any outside help beyond IP dialtone and a DHCP server.
The real market for these things is in the home. I would love to junk my crappy cordless phones and use 802.11-speaking phones on my existing wireless network. Not only would that reduce the number of boxes I have to plug in, but if it caught on it could really help reduce the persistent interference problems between 2.4GHz cordless phones and 802.11 networks.
But most people aren't going to want to run (and rely on) a PC 24/7 just to be able to make phone calls -- much less a dedicated Cisco VoIP server! And tunneling through some server on some distant network isn't going to work either, given the extra latency and decreased reliability that will introduce.
As of right now, my GPS receiver (in San Diego) shows that all of the GPS satellites it currently sees still have SA turned off. It's 1836Z on 3/19/03.
Oh I dunno, I already have a hard time telling a CDMA phone call from a regular wired call. If anything is noticeable, it's the extra delay, especially when both ends are cell phones. But the voice quality at 13kb/s is fine by me.
One could argue that the forward (base to mobile) link in regular IS-95 CDMA is not CDMA either. It's spread spectrum, but it's not multiple access since the mobiles only listen to one base station at a time (except during soft handoff, when they receive the same data from two or more base stations). Spreading the forward link simply helps the mobiles reject interference from other base stations on the same channel.
Only the reverse (mobile to base) links are truly multiple access, with one base station antenna receiving multiple mobile transmitters at the same time on the same RF channel. This is true for both IS-95 and 1xEV-DO.
So 1xEV-DO is no more (or less) CDMA than IS-95. 1xEV-DO (informally known as HDR) is based on IS-95 and uses some of the same mechanisms, but it was heavily redesigned to carry IP data rather than circuit-switched voice.
This is simply wrong, at least for California electricity. According to the "power content label" notice that SDG&E includes with my monthly electric bill, oil accounts for a negligible fraction of the electricity they sell.
California has actually built quite a few new electric generation plants over the past few years, prompted by the electricity crisis a few years ago. Of course, we now know the crisis was caused primarily by sellers like Enron "gaming" the deregulated system, and by outright fraud.
Virtually all of these new plants burn natural gas, which we do import from out of state. About half of California's electricity now comes from natural gas, and it worries me to see so much dependence on a single fuel.
Oil is a significant fuel only in the transportation sector in California. Not because it's cheap (it isn't), but because most vehicles can't run on anything else.
The only real claim for the inductive charger was its supposedly "inherent" safety. No exposed metal contacts, and all that.
The plain fact is that both inductive and conductive charging can be made quite safe against electric shock with proper grounding, interlocks and ground fault protection. As far as I know, there have been no electrocutions with either method. It's just not a problem.
The real charging safety issue turned out to be fire, not electric shock. And this affected inductive charging, not conductive. I know of two 1997 model EV1s that burned up, taking their garages with them. There were also a few more close calls. It seems that a resonating capacitor in the charge coupler aged, failed and caught fire. Because the coupler is surrounded with flammable material (foam, epoxy, etc), the fires quickly spread.
GM had already eliminated the capacitor in their redesign of the charge port in the 1999 model, but they didn't recall the 1997 models until after two destructive fires. One fire happened to a coworker, so I had a chance to investigate.
Here are my notes on that fire.
To say that GM's behavior in its aftermath was reprehensible would be an understatement. But I've now learned to expect that sort of thing from them.
I agree that fast charging is highly desirable but this is actually a strong argument against inductive charging. Inductive coupling is so inherently inefficient that even at the standard 6kW power level the charge coupler requires liquid cooling. GM kludged up a 50kW inductive charger for demonstration and PR purposes, but it required liquid coolant be pumped through the paddle as well!
While I'm sure the GM engineers thought inductive charging was a good idea at the time, experience has now shown that it is best left to electric toothbrushes. Conductive charging of EVs is the way to go. CARB made the right decision to standardize on it, even if it caused GM to take all its marbles and go home.
It's clear that your work on hybrid cars hasn't given you any special insights into environmental issues. The simple fact is that modern electric power plants -- even coal fired plants -- are far cleaner per unit of energy generated than even the cleanest gasoline engine. Just handling all that automotive gasoline -- even with vapor recovery nozzles -- releases more hydrocarbon pollution into the atmosphere than power plants do.
The only thing that even comes close to the cleanliness of a modern electric power plant is an internal combustion engine fueled by natural gas.
As for battery packs, the lead or nickel they contain is far too valuable to be thrown away. Nearly all car starting batteries are recycled, and there's no reason to believe this won't be true for EV batteries given the much larger size and cost of those packs.
Sure, current EV battery packs are large. So what? The overall vehicle is still far more energy efficient than any internal combustion engine car. Regenerative braking can recapture much of the energy associated with accelerating or lifting the car, including the battery pack mass.
You may not be aware that PG&E declared bankruptcy (and SCE came close) because they were forced to lose money on every kilowatt-hour they delivered. The PUC had capped retail rates at a time when wholesale rates were going through the roof.
So while ordinarily you'd certainly expect the utilities to favor electric vehicles, the reverse has often been true because of this perverse set of regulations.
While some of our energy comes from other sources (coal, nuclear, hydropower, etc.), the variable sources of energy are oil based. The reason we can't get alternative energy is because oil is SO cheap and plentiful.
This is wrong for two reasons, at least in California. Hardly any electricity is generated from oil here because it is just too dirty and expensive. Natural gas is the fossil fuel of choice because it is far cleaner and is (usually) cheaper. Modern combined-cycle gas-fired power plants achieve astounding efficiencies of 50-60%, far higher than any car engine.
But even where oil does fuel electric generation, it is used for peaking precisely because of its high cost. Coal, hydro and nuclear fuel costs are far lower than oil, and that's why they're used for base load generation.
First of all, this is old news. Those letters from GM are dated a year ago!
The myth that EVs just move pollutants from the tailpipe to the power plant is surprisingly persistent given that is easily refuted with hard facts. In California, EVs result in a ~97% reduction in per-mile emissions even though more than half of our electricity comes from fossil fuels (mainly natural gas). I've done the calculations myself. Because large power plants are far more efficient than automobile engines and the power grid is about 96% efficient, the overall energy efficiency of the EV is also higher.
Although I've driven EV1s for five years, I agree with CARB's decision to standardize on conductive charging. Inductive charging was a worthy experiment, but it just hasn't worked out well in practice. Inductive charging is proprietary, expensive, unreliable and inefficient. It cannot be easily scaled to the higher power levels needed to reduce charging times, which I would broaden the appeal of EVs.
GM touted inductive charging as inherently safe, but the fires that occurred in the first version of the EV1's charge port belied that claim. Electric shock hazards with both kinds of charging are essentially nil with proper grounding, interlocks and ground fault protectors.
The CARB decision to standardize on conductive charging is to be phased in over a decade, so it really had nothing to do with GM's decision to pull the EV1s off the road at the end of their current 3-year leases. GM has consistently lied and stretched the truth in their attempts to get out of the CARB ZEV mandate.
Perhaps the biggest lie by GM and the other carmakers is their claim that "no one wants EVs". This is a little strange given that GM leased virtually every EV1 they made, and there was a long waiting list when they were pulled off the market. But the success of this Big Lie can be seen in the many misconceptions and negative comments seen here and elsewhere by those who have never actually driven an EV.
Actually, on the shuttle it's MMH (Monomethyl Hydrazine). It has a slightly higher density and performance than UDMH.
UDMH is used on many other launchers, such as the Ariane. A particularly popular formulation is Aerozine-50, a 50-50 mixture of UDMH and straight hydrazine developed for the Titan. It was also used on the Apollo Lunar Module.
Actually, that's nitrogen tetroxide (N2O4), not red fuming nitric acid. I don't think RFNA has been used anywhere since the early 1960s.
The other orbiter propellants include monomethyl hydrazine (MMH), oxidized by the N2O4 in the maneuvering system thrusters, and straight hydrazine (N2H4), used as a monopropellant (decomposed by a catalyst) in the auxiliary power units to produce hydraulic power.
1xEV-DO is developed here at Qualcomm. Unlike WiFi, the links are asymmetric; different modulation methods and data rates are used on the forward (base->mobile) and reverse (mobile->base) links. This is also true for IS-95 CDMA cellular.
The 1xEV-DO forward link rate ranges from 38.4kb/s to about 2.4 Mb/s. The reverse link ranges from 9.6kb/s to 153.6 kb/s. Both rates change dynamically according to what the link can support. The overall capacity is greater than IS-95 because stronger error correction coding is used.
Have you actually tried to erase a disk drive or even a disk with a magnet? It doesn't work as well as you'd think. Modern magnetic storage devices use very high coercivity materials, which makes them very insensitive to all but the strongest fields.
I was stunned to find that the bulk tape eraser I bought at Radio Shack didn't totally obliterate the information on a 1.4MB floppy disk even though it made the disk rattle and stick to the eraser. And that's already ancient technology.
The only way to protect plaintext on a disk drive is to never write it there in the first place. Write only cipher text, and don't forget about those swap partitions. Get rid of them; with RAM as cheap and plentiful as it now is, who ever needs to swap?
This doesn't make sense. The E field of an EM wave is perpendicular to its direction of propagation, so if you have a properly tuned and aligned conductor that E field will impose a voltage across it. That's a simplified view of how any antenna works, and there's no reason to believe it shouldn't work at optical frequencies (except perhaps for the skin effect mentioned by another poster.)
Photovoltaic cells work on a very different principle. Because there's a significant amount of energy in each photon, enough to dislodge an electron from silicon's valence band into the conduction band (about 1eV), current can be generated.
If the photon lacks enough energy (has too long a wavelength), nothing happens except that the silicon heats up. If the photon is too energetic, it will still dislodge the electron but it won't impart all of its energy; the rest will again be wasted. These two effects account for much of the poor efficiency of PV cells on sunlight, which has substantial energy across the visible spectrum and into the near infrared.
I see a serious theoretical difficulty here that may explain why the optical rectenna was never built.
Sunlight at the earth's surface has a power flux density of about 1 kilowatt per square meter. To convert that to an electric field strength, we take the square root of the power flux density times the impedance of free space, 377 ohms. This gives 614 volts/meter.
Yellow light has a wavelength of 570 nm. That means the electric potential over that distance is only about 350 microvolts. This is approximately the voltage you'd see at the terminals of a 50 ohm half wave dipole, and it's far below the voltage needed to switch a rectifier. Silicon rectifiers take about 600-700 millivolts of forward bias to begin conducting, even if one could be constructed to work efficiently at optical frequencies. Germanium takes about 300 mV, and silicon Schottky diodes take about the same.
It is not possible to construct a diode that doesn't require a forward bias, otherwise we could rectify the noise from room-temperature resistors and convert ambient heat to useful work. This is specifically prohibited by the second law of thermodynamics.
If you'd like some inspiration at this, you can try listening to a
real pro. My favorite is still his call from the carpet cleaners, closely followed by the "cemetery salesman" routine.
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Thanks, I've never had to do a full-screen remote X login so I didn't know that.
Thanks, I didn't know that. I wonder if/when OpenH323 will support it, or if it's time to just switch to SIP.
SSH tunneling works so well for X that I wouldn't even mind if all IP support were removed, as long as there was still a way (e.g., UNIX domain sockets) to connect the SSH daemons to the X server and client on each end.
That said, it's still a good thing for X to support IPv6, just in case someone wants to use it. Every Internet application should support both IPv4 and IPv6.
First on the list is accessing servers behind a NAT. Wouldn't you like to connect directly to the multiple Linux boxes behind your NAT box without having to first log into the NAT and out again, or having to set up ad-hoc port forwarding kludges? Configure 6to4 on your NAT (easy if it's a Linux box) and you can establish a direct logical end-to-end IPv6 ssh connection even if the path in the middle is IPv4 only. Works great for me. I have been maintaining my parents' network in exactly this fashion for some time now.
Also on the list is VoIP. Look at all the hassles involved in running H323 from behind a NAT. (SIP may be more NAT-friendly, I haven't investigated it yet.) If only H323 supported IPv6, life would be so much easier.
But the real killer app for IPv6 will be cell phones. If cell phones are to implement true VoIP, there is simply no alternative to IPv6 because there are simply far too many cell phones in the world for the number of available IPv4 addresses.
Basically, IPv6 is all about wiping out the NAT plague and restoring the end-to-end model that originally made the Internet great. That's exactly opposite to the claim you make in your subject line. If you don't use NATs, or if you're unimaginative enough to think that you'll never need to do what they make difficult or impossible, then you probably won't be excited by IPv6. But eventually you'll probably discover why IPv6 is inevitable, even though it will have to coexist with IPv4 for a very long time.
The real market for these things is in the home. I would love to junk my crappy cordless phones and use 802.11-speaking phones on my existing wireless network. Not only would that reduce the number of boxes I have to plug in, but if it caught on it could really help reduce the persistent interference problems between 2.4GHz cordless phones and 802.11 networks.
But most people aren't going to want to run (and rely on) a PC 24/7 just to be able to make phone calls -- much less a dedicated Cisco VoIP server! And tunneling through some server on some distant network isn't going to work either, given the extra latency and decreased reliability that will introduce.
As of right now, my GPS receiver (in San Diego) shows that all of the GPS satellites it currently sees still have SA turned off. It's 1836Z on 3/19/03.
Disclaimer: I work for Qualcomm.
Phil
Only the reverse (mobile to base) links are truly multiple access, with one base station antenna receiving multiple mobile transmitters at the same time on the same RF channel. This is true for both IS-95 and 1xEV-DO.
So 1xEV-DO is no more (or less) CDMA than IS-95. 1xEV-DO (informally known as HDR) is based on IS-95 and uses some of the same mechanisms, but it was heavily redesigned to carry IP data rather than circuit-switched voice.
Phil Karn, Qualcomm
California has actually built quite a few new electric generation plants over the past few years, prompted by the electricity crisis a few years ago. Of course, we now know the crisis was caused primarily by sellers like Enron "gaming" the deregulated system, and by outright fraud.
Virtually all of these new plants burn natural gas, which we do import from out of state. About half of California's electricity now comes from natural gas, and it worries me to see so much dependence on a single fuel.
Oil is a significant fuel only in the transportation sector in California. Not because it's cheap (it isn't), but because most vehicles can't run on anything else.
The plain fact is that both inductive and conductive charging can be made quite safe against electric shock with proper grounding, interlocks and ground fault protection. As far as I know, there have been no electrocutions with either method. It's just not a problem.
The real charging safety issue turned out to be fire, not electric shock. And this affected inductive charging, not conductive. I know of two 1997 model EV1s that burned up, taking their garages with them. There were also a few more close calls. It seems that a resonating capacitor in the charge coupler aged, failed and caught fire. Because the coupler is surrounded with flammable material (foam, epoxy, etc), the fires quickly spread.
GM had already eliminated the capacitor in their redesign of the charge port in the 1999 model, but they didn't recall the 1997 models until after two destructive fires. One fire happened to a coworker, so I had a chance to investigate. Here are my notes on that fire. To say that GM's behavior in its aftermath was reprehensible would be an understatement. But I've now learned to expect that sort of thing from them.
I agree that fast charging is highly desirable but this is actually a strong argument against inductive charging. Inductive coupling is so inherently inefficient that even at the standard 6kW power level the charge coupler requires liquid cooling. GM kludged up a 50kW inductive charger for demonstration and PR purposes, but it required liquid coolant be pumped through the paddle as well!
While I'm sure the GM engineers thought inductive charging was a good idea at the time, experience has now shown that it is best left to electric toothbrushes. Conductive charging of EVs is the way to go. CARB made the right decision to standardize on it, even if it caused GM to take all its marbles and go home.
The only thing that even comes close to the cleanliness of a modern electric power plant is an internal combustion engine fueled by natural gas.
As for battery packs, the lead or nickel they contain is far too valuable to be thrown away. Nearly all car starting batteries are recycled, and there's no reason to believe this won't be true for EV batteries given the much larger size and cost of those packs.
Sure, current EV battery packs are large. So what? The overall vehicle is still far more energy efficient than any internal combustion engine car. Regenerative braking can recapture much of the energy associated with accelerating or lifting the car, including the battery pack mass.
So while ordinarily you'd certainly expect the utilities to favor electric vehicles, the reverse has often been true because of this perverse set of regulations.
But even where oil does fuel electric generation, it is used for peaking precisely because of its high cost. Coal, hydro and nuclear fuel costs are far lower than oil, and that's why they're used for base load generation.
Phil
The myth that EVs just move pollutants from the tailpipe to the power plant is surprisingly persistent given that is easily refuted with hard facts. In California, EVs result in a ~97% reduction in per-mile emissions even though more than half of our electricity comes from fossil fuels (mainly natural gas). I've done the calculations myself. Because large power plants are far more efficient than automobile engines and the power grid is about 96% efficient, the overall energy efficiency of the EV is also higher.
Although I've driven EV1s for five years, I agree with CARB's decision to standardize on conductive charging. Inductive charging was a worthy experiment, but it just hasn't worked out well in practice. Inductive charging is proprietary, expensive, unreliable and inefficient. It cannot be easily scaled to the higher power levels needed to reduce charging times, which I would broaden the appeal of EVs.
GM touted inductive charging as inherently safe, but the fires that occurred in the first version of the EV1's charge port belied that claim. Electric shock hazards with both kinds of charging are essentially nil with proper grounding, interlocks and ground fault protectors.
The CARB decision to standardize on conductive charging is to be phased in over a decade, so it really had nothing to do with GM's decision to pull the EV1s off the road at the end of their current 3-year leases. GM has consistently lied and stretched the truth in their attempts to get out of the CARB ZEV mandate.
Perhaps the biggest lie by GM and the other carmakers is their claim that "no one wants EVs". This is a little strange given that GM leased virtually every EV1 they made, and there was a long waiting list when they were pulled off the market. But the success of this Big Lie can be seen in the many misconceptions and negative comments seen here and elsewhere by those who have never actually driven an EV.
UDMH is used on many other launchers, such as the Ariane. A particularly popular formulation is Aerozine-50, a 50-50 mixture of UDMH and straight hydrazine developed for the Titan. It was also used on the Apollo Lunar Module.
Actually, that's nitrogen tetroxide (N2O4), not red fuming nitric acid. I don't think RFNA has been used anywhere since the early 1960s.
The other orbiter propellants include monomethyl hydrazine (MMH), oxidized by the N2O4 in the maneuvering system thrusters, and straight hydrazine (N2H4), used as a monopropellant (decomposed by a catalyst) in the auxiliary power units to produce hydraulic power.
All these fluids are very nasty to living things.
Well, 1xEV-DO isn't faster than WiFi. It just works over a much larger area than WiFi does. They're more complementary than competitive.
The 1xEV-DO forward link rate ranges from 38.4kb/s to about 2.4 Mb/s. The reverse link ranges from 9.6kb/s to 153.6 kb/s. Both rates change dynamically according to what the link can support. The overall capacity is greater than IS-95 because stronger error correction coding is used.
The Qualcomm website has quite a bit of detailed technical info. See http://www.qualcomm.com/cdma/1xEV/.
Have you actually tried to erase a disk drive or even a disk with a magnet? It doesn't work as well as you'd think. Modern magnetic storage devices use very high coercivity materials, which makes them very insensitive to all but the strongest fields.
I was stunned to find that the bulk tape eraser I bought at Radio Shack didn't totally obliterate the information on a 1.4MB floppy disk even though it made the disk rattle and stick to the eraser. And that's already ancient technology.
The only way to protect plaintext on a disk drive is to never write it there in the first place. Write only cipher text, and don't forget about those swap partitions. Get rid of them; with RAM as cheap and plentiful as it now is, who ever needs to swap?
Those who do not learn from history are condemned to repeat it.
Actually, a phased-array antenna is directional. It can be steered without being physically moved, though.
This doesn't make sense. The E field of an EM wave is perpendicular to its direction of propagation, so if you have a properly tuned and aligned conductor that E field will impose a voltage across it. That's a simplified view of how any antenna works, and there's no reason to believe it shouldn't work at optical frequencies (except perhaps for the skin effect mentioned by another poster.)
Photovoltaic cells work on a very different principle. Because there's a significant amount of energy in each photon, enough to dislodge an electron from silicon's valence band into the conduction band (about 1eV), current can be generated.
If the photon lacks enough energy (has too long a wavelength), nothing happens except that the silicon heats up. If the photon is too energetic, it will still dislodge the electron but it won't impart all of its energy; the rest will again be wasted. These two effects account for much of the poor efficiency of PV cells on sunlight, which has substantial energy across the visible spectrum and into the near infrared.
I see a serious theoretical difficulty here that may explain why the optical rectenna was never built.
Sunlight at the earth's surface has a power flux density of about 1 kilowatt per square meter. To convert that to an electric field strength, we take the square root of the power flux density times the impedance of free space, 377 ohms. This gives 614 volts/meter.
Yellow light has a wavelength of 570 nm. That means the electric potential over that distance is only about 350 microvolts. This is approximately the voltage you'd see at the terminals of a 50 ohm half wave dipole, and it's far below the voltage needed to switch a rectifier. Silicon rectifiers take about 600-700 millivolts of forward bias to begin conducting, even if one could be constructed to work efficiently at optical frequencies. Germanium takes about 300 mV, and silicon Schottky diodes take about the same.
It is not possible to construct a diode that doesn't require a forward bias, otherwise we could rectify the noise from room-temperature resistors and convert ambient heat to useful work. This is specifically prohibited by the second law of thermodynamics.
Perhaps "fact 1" refers only to the larger individual telemarketers, not all US telemarketers as a group? Just a thought.
Based on my own experience, "fact 2" does seems realistic.
If you'd like some inspiration at this, you can try listening to a real pro. My favorite is still his call from the carpet cleaners, closely followed by the "cemetery salesman" routine.